feat(predictive-echo): Codeman integration + Layer 4 vm tests

terminal-ui.js: _localEchoPolicy ('buffer'|'predict'|'off') computed at the
end of _updateLocalEchoState with _localEchoEnabled keeping its exact 1.12.2
values; _predictHookOnData called as a plain statement between the buffer
block and Normal Mode (visual-only, try/catch, never returns, never touches
_pendingInput); classifyPredictInput + isCodexComposerRow (baseY-based,
measured /^> /-signature gate) on CodemanTerminalInput; construction beside
the LocalEchoOverlay from the separate bundle with graceful absence;
insertTerminalText/clearTerminalInput/setFontSize/applyTerminalSkin clear or
refresh predictions. app.js: fields + tab-switch and SSE-reconnect clears.
voice-input '\r' branch and keyboard-accessory sendKey clear predictions
(both bypass onData). sendEnterKey needs no change: codex falls through to
the immediate-flush branch.

Layer 4 vm tests: classify truth table (20 cases), composer-row gate incl.
the baseY pin, policy matrix with the 1.12.2 invariants untouched, wire
neutrality + throwing-predictor pins. Stale mobile keyboard codex-buffering
tests repointed at claude; new codex twin asserts write-through streaming,
prediction spans and TTL self-heal.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/web/public/keyboard-accessory.js

@@ -601,6 +601,9 @@ const KeyboardAccessoryBar = {
    *  must be written raw to be interpreted as key presses by Ink. */
   sendKey(escapeSequence) {
     if (!app.activeSessionId) return;
+    // Arrows/Esc move the server-side cursor and bypass onData: clear
+    // predictions now instead of waiting out the ~150ms off-row grace.
+    app._predictiveEcho?.clearPredictions();
     fetch(`/api/sessions/${app.activeSessionId}/input`, {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },